"But with decade-long declines in crime, some scholars have noted a change in the nature of robberies. A 2009 study of national victim surveys taken since 1993 found that not only were robberies becoming less frequent over time, they were also becoming more violent, in part because of what the authors describe as “victim hardening.”

“Softer victims take precautions,” said Rajiv Sethi, a Barnard College economist and one of the study’s authors. In addition, he said, many people who may have become robbers in the past may instead have gotten jobs as urban economies improved, leaving the more-hardened criminals to encounter more-hardened victims on the streets of certain neighborhoods.

“You get more resistance in high-crime areas than low-crime areas,” he said. “People who would not resist have left the areas. Those who stay can’t afford to leave or to give up the little property that they have in their possession.”"

Prof. Sethi's recent research deals with credit derivatives and sovereign default, the dynamics of beliefs on networks, the economics of crime, and persistent inequality between social groups. He has also worked on the evolution of social norms and interdependent preferences, decision-making under bounded rationality, and the dynamics of asset prices in financial markets.